fix(helm)!: remove prometheus-http port declaration from coderd service spec (#12214)

This PR removes the prometheus-http port entirely from the coder service specification (originally added in #10448). It also removes the Helm value coder.service.prometheusNodePort.

Rationale: some cloud providers will helpfully expose all ports on a LoadBalancer service for you. The net effect of this is that setting CODER_PROMETHEUS_ENABLE will end up exposing port 2112 on your coderd service to the internet, which is likely undesired behaviour.

helm/coder/tests/testdata/prometheus.golden

@@ -93,14 +93,6 @@ spec:
       
       nodePort: 
       
-    
-    - name: "prometheus-http"
-      port: 2112
-      targetPort: "prometheus-http"
-      protocol: TCP
-      
-      nodePort: 31112
-      
   selector:
     app.kubernetes.io/name: coder
     app.kubernetes.io/instance: release-name